import os
'''
private attribute: start with __
'''
class Circle(object):
    '''
    hello
    '''
    __pi = 3.14
    
    def __init__(self, r):
        self.r = r

    def get_area(self):
        return Circle.__pi * self.r * self.r
    
    def __add__(self, c):
        return Circle(self.r + c.r)
    
    pass

if __name__ == '__main__':
    c1 = Circle(2)
    c2 = Circle(3)
    print(c1.get_area())
    c3 = c1 + c2
    print(c3.get_area())
    pass